JPH11240570A - Retort sterilizable paper container cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a retort sterilizable paper container cover of microwave oven adaptability. SOLUTION: A cover is used for sealing an opening of a cup-shaped paper container with a mouth edge having an opening peripheral edge curled outward and pressure bonded with upper and lower layers, and the cover 20 is constituted of a cover forming section 24 formed of a seal flange 21 placed on a mouth edge of the cup-shaped container, a peripheral wall 22 formed on a body inner wall of the cup-shaped paper container starting from the inner edge of the seal flange downwardly and an annular plate 23 formed from the lower end of the peripheral wall in parallel with the seal flange, and a cover film section 25 heat fusion bonded firmly with the peripheral wall on the upper face of the peripheral wall; and a seat plate 27 is formed on the upper face of the cover film section 25 except the section fusion bonded with the seat plate, and a pulling section 28 is formed upwardly on the end of the centerline of the seat plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover material for a paper container which can withstand reduced pressure in a container after hot filling and which can be subjected to a retort sterilization process, and more particularly to a retort sterilization process which can be reheated by a microwave oven. The present invention relates to a lid material used for a paper container having a cup shape.

[0002]

2. Description of the Related Art Paper containers which can be subjected to a retort sterilization treatment are disclosed, for example, in JP-A-57-46734 and JP-A-5-46734.
Many inventions and ideas have been disclosed, including the inventions disclosed in JP-A-8-52033 and JP-A-58-20638.

[0003] The invention disclosed in Japanese Patent Application Laid-Open No. 57-46734 discloses a synthetic resin or paper mainly composed of a thermoplastic resin excluding a high-density polyethylene resin and having a melting point of 115 ° C or higher as both outer layers. The both ends of the laminated sheet made of aluminum foil are rolled and subjected to waterproofing and welded to form a cylindrical body, and the upper and lower openings of the obtained cylindrical body are formed with the synthetic resin in the laminated sheet. A container closed with a lid made of aluminum foil whose inner surface is coated with the same kind of synthetic resin, wherein the laminated sheet is a packaging container having a laminated structure in which aluminum foil is disposed on both sides of paper. Things.

Further, the invention disclosed in Japanese Patent Application Laid-Open No. 58-52033 discloses a method in which both ends corresponding to a body seal portion of a fan-shaped or rectangular blank sheet made of a paper material subjected to a water-resistant treatment on both sides are opposite to each other over a certain width. The upper and lower parts of the body cylinder formed by folding both sides of the blank sheet so as to form a cylinder and bonding both ends at the surface having the pair of folded pieces obtained above, This is a completely water-resistant paper container sealed with a lid and a bottom plate so that the paper end surface is not exposed.

Further, in the invention disclosed in Japanese Patent Application Laid-Open No. 58-20638, the resin layer forming the inner layer and the intermediate layer made of paperboard and the like are integrally bonded, and the resin layer forming the outer layer and the intermediate layer are integrally bonded. Alternatively, the resin is bonded to each other at the upper edge of the container, the layers are degassed, and a multilayer container is formed in which an intermediate layer is sandwiched between resin layers on both sides.

[0006] However, these inventions are not suitable for microwave ovens because they all use aluminum foil, and there is still a problem in disposability because they use a lot of synthetic resins.
And so on.

[0007]

Accordingly, the present inventors have developed a retort sterilizable paper container which does not use aluminum foil and has a small amount of synthetic resin and which is suitable for a microwave oven. No. and others. An object of the present invention is to provide a lid material to be applied to these paper containers that can be subjected to a retort sterilization treatment.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, the opening edge is curled outward, and the upper and lower layers are flatly thermocompression-bonded to each other. A lid material for sealing an opening of a retort-sterilizable cup-shaped paper container having a portion, wherein the lid material is mounted on the lip portion of the cup-shaped paper container so as to be heat-fusible, A cover material forming portion including a peripheral wall provided so as to be fitted to the body inner wall of the cup-shaped paper container downward from the inner edge of the seal flange, and an annular plate provided in parallel with the seal flange from the lower end of the peripheral wall; A lid film portion that is in close contact with the peripheral wall so as to cover the opening on the upper surface of the annular plate and that is heat-sealed in close contact with the peripheral wall. And a plastic pedestal plate is provided on the center line of the pedestal plate The end is a retort sterilization treatment can be a paper container lid, wherein the tensile portion upward is provided.

[0009] In the invention according to claim 2, the lid material film portion is made of polypropylene (PP) from the outside of the container.
This is a laminated film having at least a three-layer structure in which a film, a barrier film, and a PP film are laminated in this order.

[0010] In particular, the PP film used on the inside of the container in the lid material film portion is made of polyethylene resin and P
It is obtained by forming a film by blending a P resin, an ethylene-propylene copolymer resin and a PP resin, or a blend of an ethylene-butene copolymer resin and a PP resin at a ratio of 1/9 to 3/7, respectively.

Further, in the invention according to claim 5, the PP film used on the outside of the container of the lid film portion is a polypropylene resin having a melting point of 150 ° C. or more.

In the invention according to claim 6, the barrier film constituting the lid material film portion is a film on which an inorganic compound vapor deposited thin film is formed, a film on which a metal compound vapor deposited thin film is formed, or a barrier plastic film. Is one of

[0013] In the invention according to claim 7, the lid material molded portion is obtained by injection molding a PP resin, and the PP resin has an MFR of 5 to 40 g / 10 min. Is a random-type or block-type PP resin.

[0014]

As described above, according to the present invention, the lid member has a seal flange mounted on the lip of the cup-shaped paper container so as to be heat-fusible, and the cup-shaped member extends downward from the inner edge of the seal flange. A cover material forming portion including a peripheral wall provided so as to be fitted around the inner wall of the body of the paper container, an annular plate provided in parallel with the seal flange from a lower end of the peripheral wall, and an opening on the upper surface of the annular plate. Since it is composed of a lid material film part that is heat-sealed in close contact with the peripheral wall, it absorbs the reduced pressure in the container even when cooled after hot filling with little head space, and prevents deformation of the container body Can be.

[0015] The film of the lid material is P
It is a laminated film having at least three layers laminated in the order of a P film, a barrier film, and a PP film. The PP film used inside the container is made of polyethylene resin and PP resin, ethylene-propylene copolymer resin and PP Resin or ethylene-butene copolymer resin and P
Since the film is obtained by forming a resin in which each of the P resins is blended at a ratio of 1/9 to 3/7, the fusing strength is adjusted according to the blend ratio, so that the lid material is appropriately peeled from the container body at the time of opening. Peel with strength.

Further, since the barrier film constituting the lid member film portion is formed of any one of a film on which an inorganic compound vapor-deposited thin film is formed, a film on which a metal compound vapor-deposited thin film is formed, or a barrier plastic film, It has good protection of the contents and is suitable for microwave ovens.

Further, the PP film used on the outside of the container of the lid material film portion is a polypropylene resin having a melting point of 150 ° C. or more, and the MFR of the lid material molded portion is 5 to 40.
g / 10 min. Since it uses a random type or block type PP resin, it has retort sterilization suitability.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. As shown in FIGS. 1 (a), 1 (b) and 2, for example, the lid material for a paper container capable of being subjected to the retort sterilization treatment of the present invention is placed on the edge of a cup-shaped paper container so as to be heat-fusible. Seal flange 21, a peripheral wall 22 provided so as to be fitted downwardly from the inner edge of the seal flange to the inner wall of the body 11 of the cup-shaped paper container, and a ring provided from the lower end of the peripheral wall in parallel with the seal flange. A lid material forming part 24 composed of a plate 23 and a lid material film part 25 that is heat-sealed in close contact with the peripheral wall so as to cover the opening on the upper surface of the annular plate.

A plastic pedestal plate 27 is heat-sealed on the upper surface of the lid material film portion so as to remove the heat-sealed portion with the annular plate 23. Is provided with a pulling portion 28.

The lid material forming section 24, the pedestal plate 27, and the pulling section 28 are manufactured by an injection molding method.

The material of the lid molding portion 24 is preferably a PP resin, and in particular, has an MFR of 5 to 40 g / 10 min. The random type or block type PP resin can be preferably used because of the heat resistance at the time of the retort sterilization treatment and the necessity of heat fusion with the lid film portion 25. It is preferable that the pedestal plate 27 and the pulling portion 28 are made of the same material as the lid material forming portion from the viewpoint of manufacturing described later.

The size of the lid forming portion 24 depends on the diameter of the paper container, and the height difference from the rim 12 to the lid film portion 25 serving as the top plate of the lid depends on the filling amount of the contents. And the head space is designed to be 10 cc or less.

The lid material film portion 25 is composed of a laminated film having at least three layers in which a PP film, a barrier film, and a PP film are laminated in this order from the outside of the container.

The PP film used on the inner side of the container is made of an ethylene-based olefin resin such as polyethylene resin, ethylene-propylene copolymer resin, ethylene-butene copolymer resin and PP resin in a ratio of 1/9 to 3/7. It is preferable to use a film formed from a resin obtained by blending with the above. By setting the blend ratio in the range of 1/9 to 3/7, cohesive failure occurs in the film and at the fusion interface, and an easy peeling phenomenon generally called easy peeling occurs.

The PP resin may be any of a random type, a block type and a homo type. If the blend ratio is lower than 1/9, the phenomenon of cohesive failure will not occur, and if the blend ratio is higher than 3/7, the dispersibility will be deteriorated and the dispersion of the seal strength will increase, which is not preferable.

The PP resin constituting the PP film used on the outer side of the container is a PP resin having a melting point of 150 ° C. or more, regardless of whether it is a random type, a block type, or a homo type resin during retort sterilization. It can be used because it clears heat resistance.

The barrier film constituting the lid material film section 25 is made of a base film such as a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a biaxially stretched nylon (ONy) film, or the like. 400 thin films of aluminum etc.
Although a film deposited by a method such as the vacuum evaporation method can be preferably used, a film obtained by applying a vinylidene chloride (PVDC) resin to the above substrate film may be used.

A nylon film may be interposed in the film constituting the cover film portion 25 for the purpose of reducing impact.

The lamination of the films is preferably performed by a known dry lamination method using, for example, a two-component reactive polyester adhesive.

The cover material film 25 is attached to the cover material forming part 24 by inserting the cover material film part into an injection mold in advance and injecting PP resin to form the cover material forming part. Alternatively, a method in which a lid material film portion is attached to an injection-molded lid material molding portion by ultrasonic sealing in a later process can be used.

In the case of insert injection molding, the pedestal plate and the pulling portion can be formed simultaneously with the attachment of the lid material film portion and the fusion to the upper surface of the lid material film can be performed at the same time. And the same material). When attaching the lid material film portion to the lid material forming portion in a later step, a tension portion (not shown) is provided in the lid material film portion.
In this case, there is no need to provide a PP film which is located outside the container of the lid film portion.

[0032]

EXAMPLES Examples of the present invention will be described below more specifically. <Example 1> First, a laminated film constituting the lid member film portion 25 was produced by a dry lamination method using a polyester resin-based two-component reactive adhesive in the following configuration.

[Outside of container] CPP film (propylene-ethylene block copolymer type, 30 μm thickness) / O
Ny film (15μm thickness) / PET film (12μm
m thickness), silicon oxide evaporated thin film (400Å) / PP film (propylene-ethylene block copolymer type PP
Film made of resin blended with resin and low density polyethylene (LDPE) resin at a ratio of 7/3, 50 μm
Thickness) [Inside of container]

Next, the produced laminated film is punched into a predetermined size, inserted into an injection mold for a lid material molding section, and the following grade of PP resin is injection-molded, and the retort sterilization of the present invention is performed. Processable paper container lid 20
And At the same time, injection molding of the pedestal plate and the tension portion was performed, and the pedestal plate and the tension portion were fused to the upper surface of the lid film portion.

The PP resin used was an ethylene-propylene block copolymer, melting point: 160 ° C., density:
0.90 g / cm ³ , MFR: 14 g / 10 min.

Separately, as a cup-shaped paper container suitable for the lid material, a cylindrical cup-shaped paper container having the following structure was produced.

First, a laminated sheet constituting the container body and a tape-shaped laminated film for covering the exposed end face of the container body obtained by molding the laminated sheet were dried using a polyester resin-based two-component reactive adhesive. It was produced by the lamination method in the following configuration.

Layer structure of laminated sheet, [outside container] CPP
Film (50 μm thickness) / PET film (9 μm thickness)
/ Coat layer (coating amount: 15 g / m ² ) / cup base paper (basis weight: 295 g / m ² ) / PET film (12 μm
Thickness), Silicon oxide vapor deposited thin film (400mm) / CPP film (50μm thickness) [inside of container]

Layer structure of tape-shaped laminated film, CPP film (30 μm thick) / PET film (12 μm
Thickness), Silicon oxide vapor deposited thin film (400mm) / CPP film (30μm thickness)

The CPP film used for the laminated sheet and the tape-shaped laminated film has the following constitution and physical properties.
It is a P film formed of the same type of PP resin as the PP resin used for the lid material molding section. That is, propylene-ethylene block copolymer, melting point: 160 ° C.,
Density: 0.90 g / cm ³ , MFR: 8 g / 10 mi
n. -Ethylene content: 2.5 wt%-Ethylene-butene copolymer (amorphous resin) is added to impart impact resistance.

The water content of the cup base paper is 5.0%.

In order to form a cup-shaped container from the laminated sheet, a body member blank serving as the body 11 of the container and a bottom member roll serving as the bottom 13 were prepared. Then, the tape-shaped laminated film 14 having a width of 10 mm was impulse-sealed over all exposed portions on both end surfaces to be bonded portions when the trunk member blank was formed, thereby covering the exposed portions on the paper end surface.

A cylinder having an edge portion 12 curled outward by a generally used paper cup molding machine using a body member blank in which the exposed portion of the paper end surface is covered with a tape-like laminated film and a bottom member roll. Cup-shaped paper container 10
Was molded. As a heating method, a method of locally heating and pressing the CPP film on the outside of the welded portion was adopted in order to prevent the generation of blisters due to vaporization of moisture in the cup base paper of the laminated sheet.

After the molding of the cup-shaped paper container, the edge is heated and pressed from above and below to flatten and crush it.

A hot-melted PP resin is injected into the inner wall of the bottom of the paper container, and the annular member 15 at the bottom is formed by injecting hot-melt PP resin. A paper container coated with hot-melt PP resin and capable of being subjected to retort sterilization treatment without any exposure of the paper end surface was produced (see FIG. 3). The container was coated with the PP resin by an insert injection molding method in which the hot-melted PP resin was injected into a mold in which the container was previously inserted and arranged.

The PP resin used at this time had the following constitution and physical properties. That is, ethylene-propylene block copolymer, melting point: 160 ° C., density:
0.90 g / cm ³ , MFR: 14 g / 10 min.

The diameter of the cup-shaped paper container is 58.7 m.
m, cup internal height; 85.6 mm, content: 200 m
In consideration of 1 (distilled water), 8 mm was set as the height difference from the sealing flange of the lid material to the lid film portion as the top plate so that the head space was 10 cc.

The paper container thus prepared was filled with 200 ml of distilled water at 65 ° C., and the opening was covered with the same lid, and the opening of the container body and the peripheral edge member, and the sealing of the lid were sealed. The paper container was hermetically sealed by heat sealing with a flange by an ultrasonic sealing method to obtain Example 1 (see FIG. 2).

<Comparative Example 1> The same structure as in Example 1 was used except that the film used for the lid material film portion in Example 1 was used for the lid material, and a paper container was filled with 200 ml of 65 ° C distilled water. The container was sealed to obtain a sealed paper container of Comparative Example 1 (detailed description is omitted. The head space capacity is larger than that of Example 1).

Comparative Example 2 The same configuration and shape as in Example 1 except that a 9 μm-thick aluminum foil was used instead of a PET film on which a thin film of silicon oxide was deposited as a barrier layer of a laminated sheet constituting a paper container. The container was filled with 200 ml of distilled water at 65 ° C. and sealed to obtain a sealed container of Comparative Example 2 (detailed description is omitted).

Reference Example 1 A plastic container having the same shape as that of Example 1 (PP resin / ethylene vinyl alcohol copolymer resin (EVOH) / PP resin) was used as a container, and Comparative Example 1 was used as a lid. Use the lid material used in
The container was filled with 200 ml of 65 ° C. distilled water and sealed to obtain a sealed container of Reference Example 1 (detailed description is omitted).

As described above, three types of paper containers and one type of plastic container filled with 200 ml of 65 ° C. distilled water and sealed were tested for container deformation after hot filling, suitability for retort, and suitability for microwave oven in accordance with the following methods. And evaluated.

<Experiment 1> Deformation of container after hot filling 200 ml of distilled water at 65 ° C. were filled and sealed, and four kinds of containers of Example 1, Comparative Examples 1 and 2, and Reference Example 1 were placed at room temperature (2
(3 ° C.), the container body was visually observed for deformation when allowed to cool to 3 ° C.). Table 1 shows the results. In Table 1, ○ indicates that there was no shape change such as deformation in the container body, and × indicates that the container body was dented and deformed.

<Experiment 2> Suitability of retort (1) Three containers of Example 1, Comparative Example 2 and Reference Example 1 filled with 200 ml of distilled water lowered to room temperature were manufactured by HISAKA CORPORATION under the following two conditions. Using the apparatus described in (1), an air-containing retort sterilization treatment was performed, and the presence or absence of deformation of the container after the retort sterilization was visually observed. Table 2 shows the results.

In Table 2, ○ indicates that there was no change in shape such as deformation in both the container body and the lid member, and X indicates that the lid member was dented and deformed. Condition 1 ‥‥ Initial temperature; 80 ° C., temperature rising condition; 120 ° C. reached 15 minutes Holding condition: 30 minutes, cooling time; 30 minutes Condition 2 ‥‥ Initial temperature; 80 ° C., temperature rising condition; 130 ° C. Arrival 15 minutes Holding condition: 30 minutes, cooling time: 30 minutes

<Experiment 3> Suitability of retort (2) The three types of containers of Example 1, Comparative Example 2 and Reference Example 1 were filled with the following oxygen barrier detecting material as a content instead of 200 ml of distilled water. A retort sterilization treatment was performed under two conditions, and the presence or absence of oxygen barrier properties was visually observed. Table 2 shows the results.

Oxygen barrier detecting material: A mixture of sucrose fatty acid ester, agar powder, sodium hydroxide, methylene blue, and D-glucose dissolved in hot water. Evaluation method of barrier properties. Methylene blue turns blue when exposed to oxygen. The degree of oxygen permeation is evaluated by hue using color development. In Table 2, ○ indicates that the content liquid does not develop blue and has oxygen barrier properties, and × indicates that the entire content liquid develops blue. Indicates that the oxygen barrier property has deteriorated.

<Experiment 4> Suitability of microwave oven The three kinds of containers after the retort sterilization treatment used in Experiment 2 were set in a generally used microwave oven having a rated voltage of 100 V and a rated frequency of 60 Hz under the following conditions. The suitability for microwave oven was visually observed and evaluated. Table 3 shows the results.
Shown in Microwave oven heating condition ‥‥ Heating time 3 minutes In Table 3, ○ indicates a state where reheating by a microwave oven was successfully performed, and X indicates a state where reheating by a microwave oven was not performed.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

Considering from Tables 1, 2 and 3, the container using the lid material in which the height difference between the sealing flange and the lid material film portion as the top plate is set to 8 mm so that the head space becomes 10 cc is hot. It can be seen that it can be filled, has excellent gas barrier properties, and has the suitability for retort sterilization as well as the suitability for a microwave oven after retort sterilization (Example 1).

[0063]

The cover material for a paper container of the present invention absorbs the depressurized state of the container, so that the deformation of the container is prevented and the appearance of the container is not impaired.

Further, since the PP film used inside the container is made of a blend resin whose adhesive strength is adjusted by the ratio of the ethylene-based olefin resin and the PP resin, the heat-sealed lid is used when opening. From the container with an appropriate adhesive strength.

Since a barrier film is used,
Since it has content protection properties and does not use metal foil such as aluminum foil, it has microwave oven suitability as well as retort sterilization suitability.

[Brief description of the drawings]

FIG. 1A is a plan view showing one embodiment of a lid member of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA ′.

FIG. 2 is an explanatory cross-sectional view showing a state where the lid member of the present invention is placed on a paper container and hermetically sealed.

FIG. 3 is an explanatory sectional view of a paper container capable of being subjected to a retort sterilization treatment used in Example 1.

[Explanation of symbols]

 10 cup-shaped paper container 11 trunk 12 mouth edge 13 bottom 14 tape-shaped laminated film 15 bottom incurred annular member 16 edge margin member 20 lid 21 {Seal flange 22} Peripheral wall 23} Annular plate 24} Lid material forming part 25} Lid material film part 27} Pedestal plate 28} Pull part

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B65D 81/34 B65D 81/34 N

Claims (7)

[Claims] 1. A lid material for sealing an opening of a retort-sterilizable cup-shaped paper container having an opening part whose outer periphery curls outward and whose upper and lower layers are flatly thermocompression-bonded to each other, The lid member is heat-fused on the lip of the cup-shaped paper container, and a seal flange is fitted downwardly from the inner edge of the seal flange to the inner wall of the body of the cup-shaped paper container. A lid material forming part comprising a peripheral wall provided, an annular plate provided in parallel with the seal flange from the lower end of the peripheral wall, and a lid which is heat-sealed in close contact with the peripheral wall so as to cover the opening on the upper surface of the annular plate. A plastic pedestal plate is provided on the upper surface of the lid material film portion so as to remove the fusion portion with the annular plate, and the end on the center line of the pedestal plate is upward. Retort killing characterized by being provided with a pulling portion for It can be processed paper lid for the container material. 2. The lid material film portion comprises a polypropylene (PP) film, a barrier film,
The lid material for a paper container capable of being subjected to a retort sterilization treatment according to claim 1, wherein the lid material is a laminated film having at least three layers laminated in the order of P films. 3. The PP film used inside the container in the lid film portion is a blend of a polyethylene resin and a PP resin, an ethylene-propylene copolymer resin and a PP resin, or an ethylene-butene copolymer resin and a PP resin. The lid material for a paper container capable of being subjected to a retort sterilization treatment according to claim 1 or 2, which is obtained by forming a film of the resin thus formed. 4. The blend ratio of the polyethylene resin and the PP resin, the ethylene-propylene copolymer resin and the PP resin, or the ethylene-butene copolymer resin and the PP resin, is as follows:
4. The cover material for a paper container capable of being subjected to a retort sterilization treatment according to claim 1, wherein the ratio is 1/9 to 3/7. 5. The retort sterilizer according to claim 1, wherein the PP film used on the outside of the container of the lid film portion is a polypropylene resin having a melting point of 150 ° C. or more. Cover material for paper containers that can be processed. 6. A film in which the barrier film constituting the lid material film portion is a film on which an inorganic compound vapor-deposited thin film is formed,
The retort sterilizable paper container lid material according to claim 1, 2, 3, 4, or 5, wherein the film material is one of a film formed with a metal compound deposited thin film and a barrier plastic film. 7. The lid material molding section is obtained by injection molding a PP resin, and the PP resin has a melt flow rate (MFR) of 5 to 40 g / 10 min. The cover material for a paper container capable of being subjected to a retort sterilization treatment according to claim 1, 2, 3, 4, 5, or 6, which is a PP resin of a random type or a block type.